ELI5, if it takes nearly thirty years to count to a billion, one second at a time, how are humans able design complex CPUs and Graphics cards containing multiple billions of transistors?

Question

ELI5, if it takes nearly thirty years to count to a billion, one second at a time, how are humans able design complex CPUs and Graphics cards containing multiple billions of transistors?

In: Engineering

Answer 1

Multiple people all working on different blocks

CPUs aren’t laid out by one dude just going as fast as he can, they’re modular designs. A CPU will have a cache, cores, memory controllers. The cores will have instruction units, adders, multipliers, and other blocks.

There will be design teams for each blocks, and as each block is upgraded its design just gets pasted into the bigger structure where it fits. A team might optimize a multiplier that has 10000 transistors (~2500 gates), and that adder will be copied into the 8 cores of the CPU so they impacted 80,000 transistors without having to go through and count them all

GPUs are even more of a copy paste job. While a CPU might have 8 large cores that match, a GPU will have thousands of small cores that are grouped into medium sized blocks and those blocks are connected in large groups so adding a few transistors to the design for the small core can add tens of thousands to the overall chip

For CPUs these days, the biggest driver of transistor count is CPU cache. [You can see it on the labeled die images](https://images.anandtech.com/reviews/cpu/intel/IvyBridge/review/Ivy-Bridge_Die_Label.jpg) how big of an area the L3 cache takes up, and that’s from Ivy Bridge with just 8 MB of cache. It was 27% of the 1.4 Billion transistors on the chip. Something like a 10th gen intel chip with 20 MB of cache will have an even larger percentage of the die dedicated to it.